注意這張照片是把相機用85mm鏡頭，架在三腳架上固定拍攝的，即沒有用赤道儀也沒有追蹤。
http://shannon.telecom.ksu.edu/~kaz/and ... sive-stack
我一直在思考，現時圈內個別例子，不斷鼓吹，僅數重公斤小攝星鏡，焦距不到500mm的，仍要用上比攝星鏡加相機本身還要隨時貴近倍的赤道儀及導星器，但跑到老遠長時間曝光的照片也不見得比這樣測試照好，究竟出了什麼問題？
我三四年前建議的綠色團購版HEQ5 Pro，加LVI總計才7000多元，拍攝負重可達10公斤、目視15公斤，然後大家把錢放在最好的鏡、合適的相機上，這建議到今天仍沒變。我不是搖風擺柳的人，也希望朋友買了器材後可以長期穏定發揮，甚至用了一段時間轉售仍有保有一定價值，例如用了三年以上的綠色HEQ5 Pro，轉手可能只比全新價損失數百至1000元，亦很快有人承接，而當時買入的HEQ5 Pro，據我手上資料，至今全部運作正常，新品出去時個別零件問題也全部在保養條內免費修好。
以下是拍攝者的分析：
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I imaged the andromeda galaxy a few weeks ago ( http://shannon.telecom.ksu.edu/~kaz/and ... sive-stack ). It was computed from a stack of 500 sub-expsoures. Given that it was shot at a focal length of 85mm, an exposure time of 1.3 seconds, my T2i's sensor being 22.2mm along the width, the sensor having 5,184 pixels along that width, and the Andromeda galaxy being at a declination of 41.33 degrees, I used my spreadsheet to find that individual stars moved 1.36 pixels at that declination. On a previous occasion I took a few test images of the Andromeda galaxy at 2 second exposures with all other variables being equal. I found that there was too much star trailing in my opinion. Based on my spreadsheet, the star trailing was 2.10 pixels for a 2 second exposure. Having these two references allows me to play around in the spreadsheet for other lenses and other declinations where I want to achieve the same amount of star trailing at or below 1.3 pixels.
